1. Field
The present disclosure is generally related to determining billing based on color pixels in image data.
2. Description of Related Art
Image data comprises a number of pixels having a number of components that contribute to defining the image, such as color and intensity. The image data generally includes various color or gray levels, which contribute to the intensity of each pixel in the image. Each pixel of the image is assigned a number representing the amount of light or gray level for a particular color space at that particular spot; i.e., the shade of gray in the pixel. Binary image data has two possible values for each pixel, black (represented by the number “1”) or white (represented by the number “0”). Images that have a large range of shades are referred to as grayscale images. For example, grayscale images have an 8-bit value per pixel comprising 256 tones or shades of gray for each pixel in the image (gray level of 0 to 255). Grayscale image data may also be referred to as continuous tone or contone image data. The pixels in a color image may be defined in terms of a color space, typically with three values, such as RGB—R for red, G for green, and B for blue—or four values, such as CMYK—C for cyan, M for magenta, Y for yellow, and K for black.
The pixels may also be defined in terms of device independent space (e.g., when inputting image data, such as standard RGB (sRGB) or CIE L*a*b) or a device dependent space (e.g., when outputting image data, such as RGB or CMYK). When outputting image data to an output device (e.g., copier, printer, or multi-function device (MFD)), a percentage scale may be used to identify how much ink is employed for a print or copy job. Such information may typically be used for billing a customer for print or copy jobs. For example, some methods employ a billing strategy based on an estimated amount of ink or toner consumption; others bill customers based on a print or copy mode selection (e.g., draft, standard, color, enhanced, etc.) of the output device. In dynamic print-job/copy-job environments, because printing documents using black ink or toner is less expensive than using colored ink or toner, billing is often based on the amount of color content contained in the job to be printed or copied. In order to bill customers for color printing or copying, color detection is an important feature required in an image path. Color detection is used to analyze documents for presence of color as well as an amount of color in order to bill customers accordingly. Generally, the higher the presence and amount of color in a document, the higher the cost.
Some systems include counting the number of color pixels in the image data of the document to be printed or copied. For example, a number of binary pixels associated with the CMYK color planes may be counted to determine a pixel count for each category of color at the time of marking (e.g., the time that ink(s) is/are used to mark a pixel on a page) for output in the image path. Generally, with existing color detection and counting methods, a pixel will be labeled as color when the presence of any one of the C, M, and Y signals is detected. U.S. application Ser. No. 12/252,391 (published as Patent Application No. 2010/0100505 A1 on Apr. 22, 2010), filed Oct. 16, 2008 by the same Assignee (Xerox Corporation), which is hereby incorporated by reference in its entirety, proposes a way to count color pixels. In solid ink and ink jet products, however, it is desirable to render neutral gray objects with CMYK ink. This could substantially decrease the appearance of graininess in large uniform gray areas, such as a gray fill or sweep. For billing purposes, it is not desirable to charge customer for color pixels that were (are) supposed to be gray and look gray to the human eye. The above-referenced '505 publication, for example, has limitations such as these (charging for color) in handling images that are converted to contone from rendered binary data.
In a typical multi-tier billing system for office as well as production printers or copiers, images are placed into different tiers based on the amount of color content on each page. Placing the image in the correct tier level is important both from the customer's, as well as the company's, perspective. Solid ink jet printer machines render neutral areas of an image with a combination of cyan, magenta, yellow, black (CMYK) toner/ink when printing or copying. This, however, creates problems in billing since these “gray” counts may be composed of color toners that mimic gray but may be counted towards color counts with known methods.
Some proposed solutions include methods such as disclosed in U.S. patent application Ser. No. 12/962,298, filed Dec. 7, 2010 and published as 2012/0143736 A1 on Jun. 7, 2012, and U.S. patent application Ser. No. 13/335,387, filed Dec. 22, 2011, both of which are assigned to the same assignee (Xerox Corporation) and both of which are hereby incorporated by reference in their entirety. The '298 application uses neutral pixel detection information obtained in Lab color space to control the counting of color pixels in rendered binary CMYK space. While the method disclosed in the '298 application can be effective in dealing with composite gray generated in the marking stage in solid inkjet systems, it is limited both in detection accuracy and in handling composite gray originals in the scanning process due to the relative small image processing context used in neutral pixel detection.
Also, the '387 application discloses a method of dividing the space formed by multiple color pixel counts into a number of regions and checking a set of conditions in each region to categorize the image data and use that categorization in determining the billing tier. One limitation with such a method is that, once the parameters are tuned for a particular billing tier/color area coverage relationship, they cannot be easily modified to handle requirements change without a new round of optimization.
Accordingly, an improved system and method of evaluating an image to determine an amount of color content in a document to use for billing customers is desirable.